Switch to Scala 3 enum style (#242)

* Switch to Scala 3 enum style

* Switch to scala 3 import style

README.md

@@ -166,13 +166,13 @@ sbt> console
 Once in the console, you can import your production code as such:
 
 ```
-import package.objectname._
+import package.objectname.*
 ```
 
 For example, to use functions defined in _introcourse.level01.IntroExercises_:
 
 ```
-scala> import introcourse.level01.IntroExercises._
+scala> import introcourse.level01.IntroExercises.*
 scala> add(1, 2)
 res0: Int = 3
 ```

cheat-sheet.md

@@ -131,16 +131,14 @@ The values of a product type typically contain several values, called fields. Fo
 Values of algebraic types are analysed with pattern matching, which identifies a value by its constructor or field names and extracts the data it contains.
 
 ### Sealed trait
-When defining an algebraic data type using sealed traits, it allows the compiler to exhaustively check the possible cases in match expressions.
+When defining an algebraic data type using enums, it allows the compiler to exhaustively check the possible cases in match expressions.
 The compiler will emit a warning (or an error is the option "-Xfatal-warnings" option is enabled) if you have missed a specific case.
 The compiler knows all of the subtypes of the trait that can possibly exist as they can only be extended in the file.
 
 ```scala
-sealed trait MyBooleanType
-
-case object True extends MyBooleanType
-
-case object False extends MyBooleanType
+enum MyBooleanType {
+  case True, False
+}
 ```
 
 ### Pattern matching

src/main/scala/introcourse/level02/TypesExercises.scala

@@ -175,17 +175,24 @@ object TypesExercises {
     *
     * You can read the following as a `TrafficLight` is either `Red` or `Yellow` or `Green`.
     *
-    * A sealed trait can only be extended in the same file that it is defined.
+    * A sealed trait / enum can only be extended in the same file that it is defined.
     *
     * This technique helps you make invalid states/values irrepresentable in your programs
     */
+  enum TrafficLight {
+    case Red, Yellow, Green
+  }
+
+  // Scala 2.12 equivalent syntax
+  /*
   sealed trait TrafficLight
 
   case object Red extends TrafficLight
 
   case object Yellow extends TrafficLight
 
   case object Green extends TrafficLight
+   */
 
   /**
     * scala> showTrafficLight(Red)

src/main/scala/introcourse/level03/package.scala

@@ -4,12 +4,8 @@ package object level03 {
 
   case class Person(name: String, age: Int)
 
-  sealed trait TrafficLight
-
-  case object Red extends TrafficLight
-
-  case object Yellow extends TrafficLight
-
-  case object Green extends TrafficLight
+  enum TrafficLight {
+    case Red, Yellow, Green
+  }
 
 }

src/main/scala/introcourse/level04/package.scala

@@ -4,12 +4,8 @@ package object level04 {
 
   case class Person(name: String, age: Int)
 
-  sealed trait TrafficLight
-
-  case object Red extends TrafficLight
-
-  case object Yellow extends TrafficLight
-
-  case object Green extends TrafficLight
+  enum TrafficLight {
+    case Red, Yellow, Green
+  }
 
 }

src/main/scala/introcourse/level05/EitherExercises.scala

@@ -9,13 +9,11 @@ import ExceptionExercises.personStringPairs
 object EitherExercises {
 
   //ADT for representing errors as values
-  sealed trait AppError
-
-  case object EmptyName extends AppError
-
-  case class InvalidAgeValue(value: String) extends AppError
-
-  case class InvalidAgeRange(age: Int) extends AppError
+  enum AppError {
+    case EmptyName
+    case InvalidAgeValue(value: String)
+    case InvalidAgeRange(age: Int)
+  }
 
   /**
     * In the ExceptionExercises exercise we used Exceptions to handle validation and

src/main/scala/introcourse/level06/Try.md

@@ -6,7 +6,7 @@ def evenE(n: Int): Either[String, Int] = if (n % 2 == 0) Right(n) else Left (s"$
 ```
 
 ```scala
-import scala.util._
+import scala.util.*
 
 def evenT(n: Int): Try[Int] = if (n % 2 == 0) Success(n) else Failure (new RuntimeException(s"$n is not even"))
 ```

src/main/scala/introcourse/level06/TryExercises.scala

@@ -113,7 +113,7 @@ object TryExercises {
   case class Employee()
 
   /**
-    * Now remove `import TryTestTypes._` from `TryExercisesTest.scala`
+    * Now remove `import TryTestTypes.*` from `TryExercisesTest.scala`
     */
 
   /**

src/main/scala/introcourse/level07/LogParser.scala

@@ -35,7 +35,9 @@ object LogParser {
     * - Warning
     * - Error with (severity: Int)
     */
-  sealed trait LogLevel
+  enum LogLevel {
+    case TODO // enums must have as least one case, replace this when you are ready
+  }
 
   /**
     * Now create an ADT for `LogMessage`, where `LogMessage` can be one of two possibilities:
@@ -44,10 +46,12 @@ object LogParser {
     */
   type Timestamp = Int
 
-  sealed trait LogMessage
+  enum LogMessage {
+    case TODO // enums must have as least one case, replace this when you are ready
+  }
 
  /**
-   * Once you have defined your data types, remove `import Types._` from
+   * Once you have defined your data types, remove `import Types.*` from
    * [LogParserTest.scala](src/test/scala/introcourse/level07/LogParserTest.scala)
    */
 

src/main/scala/introcourse/level07/Main.scala

@@ -1,7 +1,7 @@
 package introcourse.level07
 
 import scala.io.Source
-import LogParser._
+import LogParser.*
 
 /**
   * The `main` method does the following:

src/test/scala/introcourse/level01/IntroExercisesTest.scala

@@ -1,6 +1,6 @@
 package introcourse.level01
 
-import introcourse.level01.IntroExercises._
+import introcourse.level01.IntroExercises.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level02/TypesExercisesTest.scala

@@ -1,6 +1,7 @@
 package introcourse.level02
 
-import introcourse.level02.TypesExercises._
+import introcourse.level02.TypesExercises.*
+import introcourse.level02.TypesExercises.TrafficLight.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level03/ListExercisesTest.scala

@@ -1,6 +1,6 @@
 package introcourse.level03
 
-import introcourse.level03.ListExercises._
+import introcourse.level03.ListExercises.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level04/NullExercisesTest.scala

@@ -1,6 +1,7 @@
 package introcourse.level04
 
-import introcourse.level04.NullExercises._
+import introcourse.level04.NullExercises.*
+import introcourse.level04.TrafficLight.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level04/OptionExercises1Test.scala

@@ -1,6 +1,7 @@
 package introcourse.level04
 
-import introcourse.level04.OptionExercises1._
+import introcourse.level04.OptionExercises1.*
+import introcourse.level04.TrafficLight.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level04/OptionExercises2Test.scala

@@ -1,6 +1,6 @@
 package introcourse.level04
 
-import introcourse.level04.OptionExercises2._
+import introcourse.level04.OptionExercises2.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level04/OptionExercises3Test.scala

@@ -1,7 +1,7 @@
 package introcourse.level04
 
 import introcourse.level04.OptionExercises2.Job
-import introcourse.level04.OptionExercises3._
+import introcourse.level04.OptionExercises3.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level05/EitherExercisesTest.scala

@@ -1,6 +1,7 @@
 package introcourse.level05
 
-import introcourse.level05.EitherExercises._
+import introcourse.level05.EitherExercises.*
+import introcourse.level05.EitherExercises.AppError.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level05/ExceptionExercisesTest.scala

@@ -1,6 +1,6 @@
 package introcourse.level05
 
-import introcourse.level05.ExceptionExercises._
+import introcourse.level05.ExceptionExercises.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 

src/test/scala/introcourse/level06/TryExercisesTest.scala

@@ -1,15 +1,14 @@
 package introcourse.level06
 
-import introcourse.level06.TryExercises._
-
+import introcourse.level06.TryExercises.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 
 import scala.util.{Failure, Success}
 
 class TryExercisesTest extends AnyFunSpec with TypeCheckedTripleEquals {
   // TODO: Remove this import once you've defined Employee data type in TryExercuses
-  import TryTestTypes._
+  import TryTestTypes.*
 
   describe("parseIntSafe") {
 

src/test/scala/introcourse/level06/TryTestTypes.scala

@@ -2,12 +2,12 @@ package introcourse.level06
 
 /**
   * This file exists just to get the type-safe tests in `TryExercisesTest.scala` to compile.
-  * Once you have defined the `Employee` type in `TryExercises.scala`, remove `import TryTestTypes._`
+  * Once you have defined the `Employee` type in `TryExercises.scala`, remove `import TryTestTypes.*`
   * from `TryExercisesTest.scala`.
   */
 object TryTestTypes {
   private def undefinedInTry: Nothing =
-    throw new RuntimeException("Please remove `import TryTestTypes._` from `TryExercisesTest.scala`")
+    throw new RuntimeException("Please remove `import TryTestTypes.*` from `TryExercisesTest.scala`")
 
   def Employee(args: Any*): Nothing = undefinedInTry
 }

src/test/scala/introcourse/level07/LogParserTest.scala

@@ -1,12 +1,12 @@
 package introcourse.level07
 
-import introcourse.level07.LogParser._
+import introcourse.level07.LogParser.*
 import org.scalactic.TypeCheckedTripleEquals
 import org.scalatest.funspec.AnyFunSpec
 
 class LogParserTest extends AnyFunSpec with TypeCheckedTripleEquals {
   // TODO: Remove this import once you've defined the ADTs in LogParser
-  import Types._
+  import Types.*
 
   describe("parseIntOption") {
     it("should return the parsed integer for a valid integer") {

src/test/scala/introcourse/level07/Types.scala

@@ -2,11 +2,11 @@ package introcourse.level07
 
 /**
   * This file exists just to get the type-safe tests in `LogParserTests.scala` to compile.
-  * Once the ADTs are defined in `LogParser.scala`, remove `import Types._` from `LogParserTests.scala`.
+  * Once the ADTs are defined in `LogParser.scala`, remove `import Types.*` from `LogParserTests.scala`.
   */
 object Types {
   private def undefinedInLogParser: Nothing =
-    throw new RuntimeException("Please remove `import Types._` from `LogParserTests.scala`")
+    throw new RuntimeException("Please remove `import Types.*` from `LogParserTests.scala`")
 
   def Info: Nothing = undefinedInLogParser
   def Warning: Nothing = undefinedInLogParser